The 270 million number is repeated on the anti-Second Amendment site smartgunlaws.com, for the Law Center to Prevent Gun Violence. The link fails to mention the estimate from the Small Arms Survey was done in 2007. The data that used for the survey was collected in 2006. The estimate applies to that date, 2006. From smallarmssurvey.org:

The analysis presented here relies mostly on static data, creating only a snapshot of the global firearms balance in the year 2006. There are not yet enough dynamic, time-series reports to permit a reliable sense of how civilian holdings are developing in most countries. The general global impression, though, leaves no doubt that civilians are continually acquiring more-powerful guns. There is a connection between per capita wealth and gun ownership, which is strong enough to suggest that so long as gun ownership laws are not changed, greater national wealth leads to greater gun ownership.

Greater gun ownership may lead to greater wealth. The arrow of causality is not determined by the correlation. Uncertainty about the future also leads to more gun ownership. Private gun ownership increased over 30% during the two terms of President Barack Obama.

In 2012, the Congressional Research Service gave the number of private firearms in 2007 as 294 million, about 24 million more than the Small Arms Survey in 2006. The same document says that by 2009, the number had increased to 310 million. According to ATF reports on firearms manufacture, import and exports, the number of firearms added to the private stock were (figures rounded to .1 million):

2007 5.6 million
2008 6.9 million
2009 8.9 million
2010 8.1 million
2011 9.5 million
2012 13.1 million
2013 16.0 million
2014 12.3 million
2015 12.9 million

The estimate for 2016 is 15.6 million, based on extrapolation from the FBI National Instant Checks System (NICS).

Starting with the Small Arms Survey for the number of Firearms in the United States for 2006, the increase reported for 2007-2015 by the ATF, with the extrapolated increase from the FBI NICS system for 2016, equals another 99 million firearms. That would be 369 million firearms in the United States at the end of 2016.

If we use the Congressional Research Service number for 2007, of 294 million firearms, the estimated increase would give us 387 million firearms at the end of 2016.

Calculations using the methods developed by Newton and Zimring are well documented. They do not rely on surveys, and they include the number of modern guns added to the
stock from 1899 to 1945. Firearms manufactured before 1899 are not
included.

The
number is the cumulative addition of domestic manufacture plus
imports minus exports. It does not count guns shipped to the U.S.
military. The figures are rounded to the nearest million.

The numbers do not account for reduction of the gun stock due to wear
and tear, loss, destruction or illegal exportation; or increases of the
stock from illegal importation, individual or illegal manufacture, or
acquisition from military sources, such as surplus sales to the private market from the U.S. military.

Using the Newton-Zimring and Kleck method and ATF reported figures from 1988 to 2015, gives a total of 389 million private firearms at the end of 2015.

Extrapolation of the FBI NICS checks increases the stock by 15.6 million guns in 2016. That gives an estimate of 404 million guns at the end of 2016.

All three estimates are much higher than the 2006 numbers used for the Small Arms Survey in 2007. The larger numbers are reasonable, considering booming gun sales in the United States.

Starting with the survey data from The Small Arms Survey, at the end of 2016 there would be 369 million private firearms in the United States.

Using the Congressional Research Office figures, there would be 389 million private firearms.

Use the methods forged by Newton, Zimring, and Kleck, with ATF and FBI figures, there were 404 million firearms in the United States at the end of 2016.

The estimates are 99 to 134 million more than the outdated 2006 figure cited by The Trace.

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Background

“The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.” -- Thomas Jefferson

Syndicated columnist Charley Reese (1937-2013): "Gun control by definition affects only honest people. When a politician tells you he wants to forbid you from owning a firearm or force you to get a license, he is telling you he doesn’t trust you. That’s an insult. ... Gun control is not about guns or crime. It is about an elite that fears and despises the common people."

The rifle itself has no moral stature, since it has no will of its own. Naturally, it may be used by evil men for evil purposes, but there are more good men than evil, and while the latter cannot be persuaded to the path of righteousness by propaganda, they can certainly be corrected by good men with rifles -- Jeff Cooper (1920-2006)

Note for non-American readers: Crime reports from America which describe an offender just as a "teen" or "teenager" almost invariably mean a BLACK teenager.

We are advised to NOT judge ALL Muslims by the actions of a few lunatics, but we are encouraged to judge ALL gun owners by the actions of a few lunatics.

Two lines below of a famous hymn that would be incomprehensible to Leftists today ("honor"? "right"? "freedom?" Freedom to agree with them is the only freedom they believe in)

First to fight for right and freedom,
And to keep our honor clean

It is of course the hymn of the USMC -- still today the relentless warriors that they always were.

The intellectual Roman Emperor Marcus Aurelius (AD 121-180) said: "The object in life is not to be on the side of the majority, but to escape finding oneself in the ranks of the insane."

How much do you know about Trayvon Martin? Did you recognize him in the picture above? If not you may need to know more about him. It's all here (Backups here and here)

“An armed society is a polite society. Manners are good when one may have to back up his acts with his life.” -- Robert A. Heinlein

After all the serious stuff here, maybe we need a funny picture of a cantankerous cat